Canon's f/4 line up (17-40, 24-105 IS, and 70-200 IS) are all a few hundred dollars cheaper than Nikon's f/4 lenses (16-35 VR, 24-120 VR, 70-200 VR) but Nikon's are all newer lenses. Any new Canon lens seems to come with a decent price increase too so I wouldn't expect a new Canon 17-40 IS to be less than $1000 still.

Also, if I wanted to nitpick (and I do :-)), Nikon's 16-35 is stabilized; Canon's 17-40 is not.

Nikon's 24-120 has more range than Canon's 24-105.

Nikon's 70-200/4 VR has 5-stop stabilization vs. Canon's 4-stop IS.

And Nikon's lenses mount on my DSLR's which is the #1 reason they are better...for me, of course!